We used Sketch/Skencil code base but the percentage of this code is lower and lower. The number of SVN revisions in sK1 repository (i.e. changes in code) is more than latest Skencil SVN revision - current sK1 rev.720 but Skencil is freezed on rev.695 two years ago:

Well Igor's and Valek interview, from December of 2007 (http://www.inp.nsk.su/~baldin/interview/sK1/index.html) that is in Russian language explains why project was named as Sk1.
I'm try to translate it into English.

LXF: Why name is sK1?

Igor: sK1 - "s" it is secondary from Sketch . Upper case "K" means KDE oriented, but it doesn't means that sK1 use KDE/Qt libraries or GNOME/GTK libraries at all. The UI look and fill just looks like an KDE style, and we think that KDE open/save dialogs looks better than any another style of this kind dialogs. Though sK1 can use any style of open/save dialogs depends from platform. The color map imports from desktop manager but own can be used. The widget style is customizable and it's based on png images. Our goal is creation of application that have look like an native for each platform GNU/Linux, MacOS X, Windows
At last 1 means our current goal - develop the first version of sK1 vector graphics editor. I think It is strange to have name sK0 . If project will be useful, newest version will have new names e.g sK2, sK3 etc. Also the files ext will be changed to .sk2 etc.